The present invention relates to a method and apparatus for cleaning a polishing surface of a polisher in which a workpiece to be polished, e.g. a semiconductor wafer, is pressed against the polishing surface of a polishing cloth, a polishing abrasive wheel, etc. on a polishing table to polish the workpiece by relative motion between the polishing surface and the workpiece.
Conventionally, this type of polisher involves the problem that the residue of a polished workpiece, e.g. a semiconductor wafer, remaining on the polishing surface of the polishing cloth may damage a workpiece in the subsequent polishing process. To solve the problem, when the polishing surface of the polishing cloth is subjected to dressing by a dresser (regenerating device), a cleaning liquid, e.g. pure water, or nitrogen gas is sprayed on the polishing surface, whereby the residue of the polished workpiece on the polishing surface is discharged to the outside of the system.
When pure water is sprayed on the polishing surface as a cleaning liquid, the amount of pure water used in the entire system increases, and the amount of pure water to be supplied to a polishing unit becomes insufficient. Furthermore, pure water as sprayed on the polishing surface of the polishing cloth under low pressure cannot assist in scraping the polishing residue from the recesses in the polishing cloth surface. Consequently, it is necessary to perform dressing under a sufficiently heavy load. However, if the polishing cloth is dressed under an increased load, the stock removal of the polishing cloth by dressing increases. Thus, the polishing cloth wears out at an increased rate.
If pure water is sprayed under high pressure in order to enhance the polishing residue scraping effect, the amount of pure water used further increases, as a matter of course, causing the pure water supply to become insufficient.
Meanwhile, the method wherein nitrogen gas is sprayed on the polishing surface to blow away the polishing residue to the outside of the system is effective but has the disadvantage that the polishing residue may be dried by being sprayed with the nitrogen gas to become fixed even more firmly on the polishing cloth surface. Moreover, the spraying of nitrogen gas causes the polishing residue to scatter and contaminate the outside of the system, i.e. the surroundings of the polishing table. This exerts adverse effects upon the subsequent polishing process.
The present invention was made in view of the above-described circumstances. Accordingly, an object of the present invention is to provide a polishing surface cleaning method capable of effectively removing the polishing residue from the polishing surface of the polishing table by using a minimal amount of cleaning liquid.
Another object of the present invention is to provide a polishing surface cleaning apparatus suitably used to carry out the polishing surface cleaning method.
The present invention provides a polishing surface cleaning method for use in a polisher in which a workpiece to be polished is pressed against a polishing surface of a polishing table to polish the workpiece by relative motion between the polishing surface and the workpiece. According to the polishing surface cleaning method, a fluid mixture of a cleaning liquid and a gas is sprayed on the polishing surface to clean it.
By spraying a fluid mixture of a cleaning liquid and a gas on the polishing surface, the polishing residue on the polishing surface is scraped off by the gas in the fluid mixture and further washed away by the cleaning liquid. Therefore, the polishing residue on the polishing surface is removed almost completely. Accordingly, the polishing surface cleaned by this method is unlikely to damage a workpiece in the subsequent polishing process and can maintain stable polishing performance.
The fluid mixture may be sprayed on the polishing surface from a plurality of mixing spray nozzles provided above the polishing surface of the polishing table. The mixing spray nozzles are arranged to mix together a cleaning liquid and a gas and to spray the resulting fluid mixture.
In addition, the present invention provides a polishing surface cleaning apparatus for use in a polisher in which a workpiece to be polished is pressed against a polishing surface of a polishing table to polish the workpiece by relative motion between the polishing surface and the workpiece. The apparatus includes a mixing spray nozzle for mixing together a cleaning liquid and a gas and for spraying the resulting fluid mixture on the polishing surface to clean it.
By spraying a fluid mixture of a cleaning liquid and a gas on the polishing surface from the mixing spray nozzle, the polishing residue on the polishing surface is removed almost completely. Accordingly, the polishing surface cleaned by this apparatus is unlikely to damage a workpiece in the subsequent polishing process and can maintain stable polishing performance.
The polishing surface cleaning apparatus may further include a pressure controller for independently controlling the respective pressures of a cleaning liquid and a gas supplied to the mixing spray nozzle.
The provision of the pressure controller allows desired control of the ratio between the cleaning liquid and the gas in the fluid mixture and the spray speed of the fluid mixture and enables the cleaning action on the polishing surface and so forth to be controlled as desired.
In the polishing surface cleaning apparatus, the mixing spray nozzle may be secured to a mounting member for mounting an abrasive liquid supply nozzle for supplying an abrasive liquid to the polishing surface or a chemical liquid supply nozzle for supplying a chemical liquid to the polishing surface.
The foregoing and other objects, features and advantages of the present invention will be apparent from the following detailed description and appended claims taken in connection with the accompanying drawings.